In 2013, 39% of all Northern Ireland exports went to the Republic of Ireland.

In a statement to the BBC, Mr Ennis said: "Given there is no clarity on what the future relationship between the UK and EU will look like, or what policies the UK will pursue, the potential upside of an exit in the long term is impossible to objectively assess."

But he added that there would be "uncertainty" for business "during any transition period".

An Invest NI spokesperson made clear Mr Ennis was only representing the board's position.